A polymer electrolyte fuel cell (hereafter also referred to as “PEFC” as needed) generates electric power and heat simultaneously by causing a fuel gas containing hydrogen and an oxidizing gas containing oxygen such as air to undergo an electrochemical reaction in the fuel cell.
The fuel cell has a membrane electrode assembly, referred to as “MEA.” The MEA is sandwiched by a pair of conductive separators (specifically, a pair of separators comprising an anode separator and a cathode separator) so that gaskets are disposed on the peripheral edge portions of both sides of the MEA.
The PEFC generally has a structure in which MEA units are stacked between a pair of conductive separators to form a plurality of rows.
A serpentine-type fuel gas passage region through which a fuel gas (which is, of the reaction gas, a gas containing a reducing agent supplied to the anode) passes is formed on the surface of the anode separator so as to connect a fuel gas supply passage (a fuel gas supply manifold port) and a fuel gas discharge passage (a fuel gas exhaust manifold port). The fuel gas passage region is constituted by a plurality of fuel gas passage grooves formed so as to connect the fuel gas supply passage and the fuel gas discharge passage. The plurality of fuel gas passage grooves are bent in a serpentine shape so that they are laid parallel to one another, whereby the just-mentioned serpentine-type fuel gas passage region is formed.
A serpentine-type oxidizing gas passage region through which an oxidizing gas (which is, of the reaction gas, a gas containing an oxidizing agent supplied to the cathode) passes is formed on the surface of the cathode separator so as to connect an oxidizing gas supply passage (an oxidizing gas supply manifold port) and an oxidizing gas discharge passage (an oxidizing gas discharge manifold port). The oxidizing gas passage region is constituted by a plurality of oxidizing gas passage grooves formed so as to connect the oxidizing gas supply passage and the oxidizing gas discharge passage. The plurality of oxidizing gas passage grooves are bent in a serpentine shape so that they are laid parallel to one another, whereby the just-mentioned serpentine-type oxidizing gas passage region is formed.
With the above-described configuration, while the fuel gas is flowing through the passage grooves in the fuel gas passage region and while the oxidizing gas is flowing through the passage grooves in the oxidizing gas passage region, the reaction gas (power generation gas) is supplied to the MEA and is consumed by the electrochemical reaction inside the MEA.
Aiming at commercialization of PEFCs, the configurations of anode separator and cathode separator for realizing a better flow condition of the reaction gas to make a more stable electric power generation possible have been desired, and various attempts have been made to achieve the configurations (see Patent References 1 to 4).
For example, a separator provided with a reaction gas flow merge region at a turn portion of a plurality of passage grooves for merging the passage grooves has been proposed, which is intended to improve drainage performance of the condensed water generated in the passage grooves sufficiently, enhance gas dispersion performance of the reaction gas from the passage grooves to a gas dispersion electrode, reduce passage resistance (pressure loss), and so forth (see, for example, Patent References 2 and 4). In the flow merge region of the passage grooves, a plurality of protrusions in a dotted form are provided on the bottom face of a concave portion connected to the plurality of passage grooves.
In addition, a separator in which the number of passage grooves changes (reduces) as the passage grooves are closer from reaction gas supply passage (gas inlet side) to the reaction gas discharge passage (gas outlet side) has been proposed, which is aimed at improving the drainage performance of the above-mentioned condensed water, improving gas dispersion performance, and reducing the size effectively (see, for example, Patent References 1 and 3).    Patent Document 1: Japanese Unexamined Patent Publication No. 11-250923    Patent Document 2: Japanese Unexamined Patent Publication No. 10-106594    Patent Document 3: Japanese Unexamined Patent Publication No. 2000-294261    Patent Document 4: Japanese Unexamined Patent Publication No. 2000-164230